Since the nuclear magnetic resonance groundwater detection technology is a unique geophysical method with which the groundwater can be directly detected presently, it has been widely used in groundwater resources exploration, advanced prediction of mine/tunnel disaster water source, seawater intrusion and the like. However, the existing nuclear magnetic resonance water detection instrument operates in response to excitation of a magnetic source (coils), hence it is difficult to achieve a large area measurement at a single time, and the detection efficiency is low.
In the published CN102096112, titled “Array coil-based nuclear magnetic resonance groundwater detection instrument and field detection method”, multiple coils function as receiving antennas, thereby achieving a 2D/3D detection on the groundwater.
With the published CN103033849, titled “Multi-channel nuclear magnetic resonance groundwater detection instrument and field work method”, not only the 2D/3D detection can be achieved, but also the anti-noise capability of the instrument is further improved with reference coils.
In the published CN1936621, titled “Nuclear magnetic resonance and transient electromagnetic combined instrument and method”, two types of geophysical methods, i.e., transient electromagnetic and nuclear magnetic resonance are combined. As compared with the method based on only the nuclear magnetic resonance, a detection depth and a detection accuracy are effectively improved with the method disclosed in CN1936621. However, all of the above three methods are based on magnetic source excitation, a maximum detection area for each detection point depends on a side length of a transmission coil (the maximum side length is 150 m), and a measurement duration for each detection point is 46 minutes, hence the detection efficiency is low.